Producing isoprene.



To all whom it may concern:

rr SATES ATENT ornron.

OTTO GBAUL AND GOTTFRIED HANSCHKE, OF LUDWIGSHAFEN-ON-THE-RHINE, AND FRANZ WEBEL, 0F MANNHEIM, GERMANY, ASSIGNORS, BY MESNE ASSIGNMENTS.

TO ALIEN PROPERTY CUSTODIAN.

I PRODUCING- ISOPRENE.

1,298,929. No Drawing.

Be it known that we, OTTO GRAU'L, Go'r'r- FRIED HANSCHKE, and FRANZ WEBEL, subjects, respectively, of the Grand Duke of Anhalt, of the King of Prussia, and 0f the King of Bavaria, residing, respectively, the first two at Ludwigshafen-on-Rhine and the third at Mannheim, Germany, have invented new and useful Improvements in Producing Isoprene, of which the following is a specification. i

We have discovered that we can obtain isoprene while starting from a mineral product which is available in any quantity desired,viz. from isopentane, in an excellent yield and in a pure condition as hereinafter described. Accord ng to our lnvention 1S0- pentane is first treated with a halogenizing agent, so as to introduce one atom of halogen into the isopentane molecule, and then the product (which generally consists of a mixtureof two mono-halogen isopentanes) is treated with an agent which will split off halogen hydrid, homogeneous trimethylethylene being the result. This homogeneous trimethyl-ethylene can be obtained directly from the mixture of mono-halogen isopentanes owing to the surprising action of said agent which both splits off the halogen hydrid and also causes the re-arrangement of isomeres formed to take place. The trimethyl-ethylene thus obtained is then treated with a,.halogenizing agent, so that one molecular ":proportion of halogen is added, and the isoeamylene-dihalogenid thus produced is then treated with an agent which is capable of splitting off two molecular proportions of halogen hydrid. Agents splitting off halogen hydrid either chemically or by catalytic'action are suitable in this and also in the former stage of the mono-halogen compound with a body which process.

This transformation of dimethyl-allene is described in detail and claimed in the speci fication of U. S. Patent 1,083,164, consequently we do not claim in this application this step by itself.

Specification of Letters Patent.

p of splitting o Patented Apr. 1, 1919.

Application filed February 5, 1912. Serial No. 675,656.

an outlet for the hydrochloric acid formed and also with an arrangement for returning unaltered isopentane to be reacted upon again, while the crude chlor-isopentane can be drawnoff and, if desired, can be subjected to distillation. Then, at a temperature of about four hundred and fifty degrees centigrade, pass the mono chlor isopentane through a tube filled with an excess of gran,- ulated caustic lime, whereupon hydrochloric acid is split off and trimethyl-ethy'lene is produced in very good yield, isomeric olefins formed bein converted in the same operation into trlmethyl-ethylene by the action of the hot lime. The trimethyl-ethylene is then treated with bromin and thus converted into the dibromid, which is passed slowly over catalytic material, such for instance as barium ch-lorid or aluminium oxid, at a pressure of about 20 millimeters of mercury and at a temperature of about 350 0. Extract, by means of alkali, the from the vapors obtained and then pass the remainder through a cooled vessel in order to condense the isoprene.

is capable of splitting oif halogen hydrid, then treating the product with a halogen, so as to produce dihalogen isopentane, then treating this roduct with a body capable halogen hydrid.

hydrobromic acid 2. The process of producing isoprene by set our hands in the presence of two sub- 10 monochlorinating isopentane, isolating the scribing witnesses.

monochlor -isopentane from unaltered iso- OTTO GRAUL pentane then heatlng the monochlor lsopen- 5 tane with an excess of caustic lime, then treating the trimethyl-ethylene with bromin,

and then passing the trimethyl-ethylene di- Witnesses:

bromid over heated barium chlorid. J r ALEC LLOYD, In testimony whereof we have hereunto A. O. TITTMAN. 

